A comparative study on single-laser and multi-laser selective laser melting AlSi10Mg: defects, microstructure and mechanical properties

AlSi10Mg samples fabricated by using a multi-laser beams selective laser melting system have been studied in this paper. The relative density, defects, microstructure and mechanical properties of the isolated and overlap samples are investigated. It is found that the width and depth of the melt pools in overlap area are larger than that in isolated area, which leads to an obvious boundary between the overlap area and isolated area. Moreover, a few small pores were found in the melt pools along the overlap boundary. The isolated and overlap area in as-built samples have similar microstructure, microhardness and tensile strength. The morphology and distribution of Si change into particles from continuous dendrite after annealing treatment. However, it does not cause the grains to grow up. The microhardness and tensile strength have little difference due to almost the same grain size. The slight difference in strength and elongation of isolated and overlap samples are supposed to be caused by small pores. It can be concluded that the microstructure significantly influences the microhardness and strength of the AlSi10Mg samples, while the small pores have limited influence. There area few smooth surfaces on the fractures of both isolated and overlap samples, which turn out to be the melt pool boundaries. This indicates that the cracks mainly propagate along the melt pool boundaries.